Aspheric lens and method for making same

ABSTRACT

An aspheric lens ( 1 ) includes a substrate ( 10 ) and an aspheric film ( 12 ). The substrate ( 10 ) is made of glass, and has a spherical surface ( 102 ). The aspheric film ( 12 ) is formed on a surface of the substrate ( 10 ), and is made of plastic material. The aspheric film ( 12 ) has an aspheric surface ( 122 ). A method for making the aspheric lens ( 1 ) includes the steps of: providing a substrate ( 10 ) made of glass, the substrate ( 10 ) having a spherical surface ( 102 ); putting the substrate ( 10 ) in an injection mold, the injection mold having an aspheric surface ( 202 ); closing the injection mold, and injecting a plastic material on the substrate ( 10 ); solidifying the plastic material, thereby forming an aspheric film ( 12 ) on the substrate ( 10 ); and opening the injection mold, and obtaining the aspheric lens ( 1 ).

FIELD OF THE INVENTION

The present invention generally relates to lenses such as those used inportable electronic devices, and more particularly to aspheric lenses.

BACKGROUND

Currently, digital camera modules are included as a feature in a widevariety of portable electronic devices. Most portable electronic devicesare becoming progressively more miniaturized over time, and digitalcamera modules are correspondingly becoming smaller and smaller.Nevertheless, in spite of the small size of a contemporary digitalcamera module, consumers still demand excellent imaging. The imagequality of a digital camera is mainly dependent upon the opticalelements of the digital camera module.

Aspheric lenses are very important elements in the digital cameramodule. An aspheric lens can easily focus an image on an imaging point,because the aspheric lens can attain different refractive index by meansof selected different materials and profiles. Therefore an aspheric lenscan avoid many of the image-forming problems of spherical lenses. Inaddition, with a single aspheric lens, the number of lens pieces in thecamera can be reduced. Thus the cameras can have reduced size. Two ormore aspheric lenses are used in some cameras for high quality imageforming. Contemporary aspheric lenses are made of plastic or glass.Glass aspheric lenses are generally manufactured by way of glassmolding. A glass molding machine operates at a high temperature and highpressure during the glass molding process. Therefore the cost of glassaspheric lenses is relatively high. Plastic aspheric lenses aregenerally manufactured by way of injection molding. Though the cost ofplastic aspheric lenses is relatively low, the plastic aspheric lens haslow image-forming quality compared to a glass aspheric lens. This isbecause the transparency of the plastic is lower than that of glass.

What is needed is an inexpensive aspheric lens which provides highimage-forming quality in camera.

SUMMARY

An aspheric lens includes a substrate and an aspheric film. Thesubstrate is made of glass, and has a spherical surface. The asphericfilm is formed on a surface of the substrate, and is made of plasticmaterial. The aspheric film has an aspheric surface.

A method for making an aspheric lens comprises the steps of: providing asubstrate made of glass, the substrate having a spherical surface;putting the substrate in a injection mold, the injection mold having anaspheric surface; closing the injection mold, and injecting a plasticmaterial on the substrate; solidifying the plastic material, forming anaspheric film on the substrate; opening the injection mold, and gettingan aspheric lens.

Other objects, advantages and novel features will become more apparentfrom the following detailed description when taken in conjunction withthe accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an aspheric lens in accordance witha preferred embodiment of the present invention; and

FIG. 2 is a cross-sectional view of an injection mold in accordance witha preferred embodiment of the present invention, the injection moldbeing used to make the aspheric lens of FIG. 1.

DETAILED DESCRIPTION OF PERFERRED EMBODIMENTS

Referring to FIG. 1, in a preferred embodiment of the present invention,an aspheric lens 1 comprises a substrate 10 as its main portion and anaspheric film 12. The aspheric film 12 is formed on a spherical surface102 of the substrate 10. The substrate 10 is made of glass material.Therefore the substrate 10 can be obtained at an economical price.Further, the substrate 10 can be made by means of finishing or whetting.The aspheric film 12 has an aspheric surface 122. The aspheric film 12is made of transparent plastic material such as polycarbonate,polymethyl methacrylate, or a combination thereof. The substrate 10 andthe aspheric film 12 preferably have the same refractive index, foroptimal image-forming quality. The aspheric film 12 is preferablyrelatively thin, because plastic material has lower transparency thanglass material. Therefore the width of the aspheric film 12 ispreferably 10-900 microns, and even more preferably 50-500 microns.

Referring also to FIG. 2, in a preferred embodiment of the presentinvention, a method for making an aspheric lens comprises the steps of:

-   -   (1) providing a substrate 10 made of glass material, the        substrate 10 being made by means of ordinary surface treating        method;    -   (2) providing an injection mold including a core insert 20, the        core insert 20 having an aspheric surface 202 and being made of        a material selected from the group consisting of stainless        steel, high rigidity steel, nickel phosphide (NiP), and any        combination thereof;    -   (3) cleaning the substrate 10, and putting the substrate 10 in        the injection mold;    -   (4) closing the injection mold, and injecting transparent        plastic material such as polycarbonate or polymethyl        methacrylate in the injection mold, wherein the operational        temperature is 100-300° C., and the operational pressure is        200-100 newton;    -   (5) solidifying the plastic material with ultraviolet light,        thus forming an aspheric film 12 on a spherical surface 102 of        the substrate 10; and    -   (6) cooling the injection mold, thereby obtained the aspheric        lens 1.

It is believed that the present embodiments and their advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. An aspheric lens, comprising: a substrate made of glass; and anaspheric film formed on a surface of the substrate, the aspheric filmbeing made of plastic, and the aspheric film comprising an asphericsurface.
 2. The aspheric lens as claimed in claim 1, wherein the plasticis a material selected from the group consisting of polycarbonate andpolymethyl methacrylate, and any combination thereof.
 3. The asphericlens as claimed in claim 1, wherein the aspheric film has a thickness inthe range of 10-900 microns.
 4. The aspheric lens as claimed in claim 1,wherein the aspheric film has the same refractive index as that of thesubstrate.
 5. A method for making an aspheric lens, comprising the stepsof: providing a substrate made of glass; putting the substrate in aninjection mold, the injection mold having an aspheric surface; closingthe injection mold, and injecting a plastic material on the substrate;solidifying the plastic material, thereby forming an aspheric film onthe substrate; and opening the injection mold, and obtaining theaspheric lens.
 6. The method according to claim 5, wherein the injectionmold has a core insert, and the core insert has an aspheric surface. 7.The method according to claim 6, wherein the core insert is made of amaterial selected from the group consisting of stainless steel, highrigidity steel, nickel phosphide, and any combination thereof.
 8. Themethod according to claim 5, wherein the injection mold has anoperational temperature in the range of 100-300° C.
 9. The methodaccording to claim 5, wherein the injection mold has an operationalpressure in the range of 200-1000 newton.
 10. The method according toclaim 5, wherein the plastic material is solidified by ultravioletlight.
 11. A method for making an aspheric lens, comprising the stepsof: forming a glass substrate as a main portion of said aspheric lens;and forming an aspheric film on a side of said glass substrate so as todefine an aspheric surface on said film facing away from said glasssubstrate.
 12. The method according to claim 11, wherein said asphericfilm is made of plastic selected from the group consisting ofpolycarbonate, polymethyl methacrylate, and any combination thereof. 13.The method as claimed in claim 11, wherein said aspheric film has thesame refractive index as that of said substrate.